From semiconductor lasers to fiber Bragg grating lasers in optical communications.

摘要

This thesis describes the semiconductor laser signal and noise propagation effects in single mode fiber and fiber Bragg gratings. The capability to fabricate custom fiber Bragg gratings was developed, which enabled the design and fabrication of gratings for a number of applications. Finally, gratings were developed and specialized for use in a single mode fiber ring laser.; A quantum mechanical description of laser noise is used to discuss sub-shot noise operation, called squeezing, and was measured for an 850 nm Fabry-Perot semiconductor laser at room temperature. With slight temperature tunings, higher sidemode suppression correlated with lower noise.; Noise analysis was performed with 1540 nm distributed feedback semiconductor lasers. Laser parameters such as noise, chirp, and resonance frequency were characterized by propagation in dispersive fiber and fitting the parameters to a model for the laser and fiber. A correlation was found between side mode suppression and laser noise, especially, after several kilometers of propagation in fiber.; Facilities were established to produce customized fiber Bragg gratings in various fiber types and glasses for applications including ion-exchanged waveguides, dispersion compensation, noise reduction, beam or pulse shaping, and spectral filtering for dense wavelength division multiplexed (DWDM) optical networks. Theory and experiment indicated direct laser modulation enhancement by a uniform fiber Bragg grating by 7 dB at modulation frequencies up to 25 GHz and noise reduction of 2 dB from 0–15 GHz.; Fiber gratings were refined for use as key elements in a new type of single mode fiber ring laser. Beneficial characteristics of this fiber laser include long cavity size (80 cm), 80 dB signal-to-noise ratio, high side mode suppression ratio, nearly shot noise limited amplitude noise, and white noise linewidth as narrow as 2 kHz. Thus, extremely low noise enhancement was observed after 50 kin of standard, dispersive fiber up to 20 GHz. A comparison was made between our fiber ring laser and a high grade distributed feedback semiconductor laser in transmitting 10 Gbits/sec data. After 50 km of fiber, the fiber ring laser achieved the same signal to noise ratio with half the power as the semiconductor laser.